Voltage Endurance Testing Stator insulation systems for inverter-fed machines

There is an industry need for suitable methods to qualify medium- and high-voltage stator-insulation systems for inverter duty applications. The technical specification (TS) International Electrotechnical Commission (IEC) 60034-18-42 has been written to address the unique requirements of form-wound micaceous systems to withstand inverter pulses characterized by elevated voltage, fast rise times, and high-frequency impulse-repetition rates. These machines do not operate under the same aging conditions as those supplied by sinusoidal power or as motors with random wound stators supplied by pulsewidth modulated (PWM) drives. Depending on the specific waveform characteristics observed at the machine terminals, the ground-wall PE: Please note that the correction given to close up "Ground-wall" has been ignored. Kindly confirm, insulation, turn insulation, slot-corona suppression, and end-winding voltage-grading systems are significantly affected by aging factors such as partial discharge (PD) and elevated temperature. The TS offers technically sound guidelines to manufacturers and users describing test procedures to prove the electrical and thermal reliability of these components. Like IEC 60034-18-41 for low-voltage systems, the new technical specification will significantly impact construction and testing of National Electric Manufacturing Association (NEMA) motors. This article describes the theoretical and practical considerations of the specification. © 2009 IEEE.